Letter 28061

Problems with electrocoat bath [Brazil] 

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In the electrocoat bath, which they are the possible deposition bad causes in some pieces and the appearance of pitting in other, being that the problems appear randomly.

Thanks,

Diogo Cavalcanti
technical chemist - Caxias do Sul, RS, Brazil

I think your question is hopelessly broad, Mr. Cavalcanti; but if anyone disagrees and wants to answer, we'll be happy to print their reply.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

Difficult to answer too broad of a question. Need more details. I would be checking the conductivity and pH of the bath and the rinses to look for ionic contamination. Check you temperature as well as too hot and the conductivity will skyrocket. Get a pH and conductivity from you water supply as well.

Also check the solids in all baths to see if you might have too much dirt and/or solids. How much filteration do you have on the system and how often do you change the filter bags? Other than that verify that your ultrafilter in running right and call you paint supplier and ask if there is anything specific to your material you need to know.

Michael Brown
chemical company - Columbus, Ohio, USA

Pitting in e-coats can be due to many reasons, such as bath contamination, the bath being out of specification, poor or insufficient substrate pretreatments, dissolved gas in the bath etc etc. It is sometimes maneifested as "fish eyes" and is a common complaint in many organic coating systems. I think we need more information and perhaps some pictures.

Trevor Crichton R&D practical scientist - UK

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